Demand apparatus.



L'T. DEMPSTER.

DEMAND APPARATUS.

APPLICATION FILED 0120.7. 1914.

Patented May 11, 1915.

Z SHEETS-SHEET I. Flgg. I.

Inventor:

John T. Dempster,

J. T. DEMPSTER.

DEMAND APPARATUS.

APPLICATION FILED DEC.7.19|4.

1,139,169. Patented May11,1915.

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Witness es: Invent or:

John T. Dempsiger.

State of UNITED STATES PATENT OFFICE.

JOHN T. nnmrsrrnn, or SCHENECTADY, new YORK,

- COMPANY, a CORPORATION or ASSIGNOR T0 GENERAL IEELEG'JI'RIC NEW YORK.

DEMAND APPARATUS.

Specification of Letters Patent.

Patented May 11, 1915.

Application filed December 7, 1914. 7 Serial No. 875,802.

- upon a central generating station.

More particularly my invention relates to apparatus for recording the abnormal demands made by an electrical installation with special regard to the frequency of 00- currence and the magnitudeof abnormally large demands, and more especially the magnitude of the maximum demand of the installation.

A problem of particular importance in the present day distribution of electrical energy to individual consumers is to determine the tariff rate which should be charged each consumer for the energy he uses. The most logical method for determining this tariff rate consists in basing the rate upon the character and magnitude of the demand made upon the central generating stations plant by the consumers installation. This method obviously necessitates the provision of an apparatus which will record the magnitude of the consumers normal demand, the character of the demand, that is Whether substantially constant or fluctuating, and if fluctuating the frequency of occurrence and the magnitude of the abnormal demands and in particular the abnormally large demands. i

Another method of determining the tariff rate for electricalenergy, which is regarded with considerablefavor, consists incharging the consumer a certain contract rate for the energyused, provided the demand does not exceed a predetermined amount. If the demand at any time exceeds this predetermined amount, the consumer is penalized;

the amount of the penalty depending upon the magnitude of the greatest or maximum demand made by his installation. This method requires for its successful operation an apparatus which'willaccurately record the greatest or maximumdemand the consumers installation.-

A curve drawing instrument gives a sub stantially complete record of the consumers demand during the time of the instruments operation, and if properly designed for this particular purpose is the most satisfactory instrument to employ for obtaining the information necessary to determine .the proper tariff rate. since the central station is generally onlyparticularly interested in the ab: normally large demands of an electrical installation, it is evident that the larger portion of the record of the curve drawing instrument could be eliminated or greatly condensed without injuring its utility as a basis for determining'tariff rates.

To this end, the object of my present invention is to provide a novel and improved construction of apparatus adapted for use in place of a curve drawing instrument; for determining tariff rates demands made by an electrical installation upon the central generating stations plant.

The object of my invention is then to provide a novel and improved form of demand apparatus, and particularly to provide an apparatus'which will record the demand of an electrical installation in an accurate, satisfactory and convenient form.

A further object of my invention is to generally improve the construction and operating mechanism of demand apparatus.

Other objects of the invention will be apparent to those skilled in the art from'the following specification and appended claims. The novel features which I believe to be patentably characteristic of my invention are definitely indicated .in the. claims appended hereto. The construction and, mode of operation of an apparatus embodying .my invention made by and which records: in a simple and convenient form the general means particularly adapted for use in this type of apparatus; Fig; 4t, is a diagrammatic view in perspective of a modified construe tion of demand apparatus embodying my invention; and Figs. 5 and 6 are detail views of the circuit-controlling means illustrated in the apparatus of Fig. 4. I

The object of penalizing a consumer when the demand of his installation exceeds a predetermined amount is ordinarily to induce him to maintain his normal ener consumption or normal demand below t is predetermined amount. It is not proposedto penalize the consumer for temporary overloads or for the eflects of unusual overloads of very short duration such as short circuits. Accordingly, it is always desirable in determining the demand and particularly the maximum demand to employ a substantial time interval for the measurement of'the demand. The average demand of a consumers installation may among variousmethods be obtained by measuring the amount of energy consumed during a predetermined time interval, or by measuring the time required \to consume a predetermined quantity or'1nthe well known worm shaft.

terval of energy. In either casethe demand "is measured du'rlng each of a plurality 'of successive intervals of-reference, whether of time or energy, and the average-demand.

during any interval of reference is the aver-* of energy consumption during that age rate interval. In either case the time interval durin which the demand is being measured shoul be of substantial length, that is one minute or greater. While'the demand apparatus which I have illustrated in the accompany drawings is'particularly designed to measure a consumers demand in terms .of the amount of ener consumed during a redeterniined time interval, it will be evidentto those skilled in the art that certain features of my applicable totan apparatus which measures the demand in terms of thetime required to consume a predetermined quantity of eneferring first to Fig. 1 ofthe drawings, there is diagrammatically represented a rotatable meter shaft 10. The meter itself forms no part of my present invention and "'rmay be any one of the well known types of motor meters. Rotation of the meter shaft 10 is transmitted by electromagnetic means to a vertically positioned screw-threaded shaft 11 The shaft 11 is pivotally mounted and in ts action in the apparatus resembles A ratchet 12 1s secured to the lower end of the shaft 11. and is adapted to be driven by a pawl 13. A spring brake 34: bears against the ratchet 12 and accurately limits movement of the ratchet in response to the driv ng action of the pawl. The pawl 13 is. pivoted at 14 to aarri 15 secured to a rod 16 A spring present invention ,are equally sulating material, such aS ivory,

17 normally forces the pawl against a stop pin 18 secured to the carriage. A second rod 19 extends parallel to the rod 16 and has secured thereto a magnetic plunger armature member 20 coo crating with a pair of electromagnetsof the solenoid type. The rods 16 and 19 are secured together by end members 21 and 31. A single electromagnetic winding'of the solenoid type having two sectionsobtained by bringing out a common tap from the middle-point of the winding or two independent solenoid windings In the drawings Ihave illustrated byway "of example two independent electromagnetic or solenoid windings 22 and.

24. The armature20 is so designed and related to the two windin s that when current causes the armature and the elements secured thereto to move toward the right until the armature enga initial position of he armature 20 is determined by its engagement with the fixed stop 23, which is theposition of the armature indicated in-Fig. 1 of the drawings, Energization of the winding-'22 causes the-armature to move toward the left, whereupon the ,pawl 13 operatively' engages the ratchet 12 and turns the shaft 11 through an angle cor-- responding to one tooth pitch of the ratchet. Energization of the winding 24 causes the ar'matureto move toward the right, and thus efiects the. return of'the armature to its initial position.

The solenoid windings are adapted to be- .supplied with current from direct current The electric circuit of each Wind- 'ing is controlled by a circuit-closing device mains 26.

embodied in the shaft 10, the construction of which is illustrated in detail in Figs. 2 and 3 of the drawings. The circuit of each winding is further controlled by a switching device operatively related to the armature member 20. A conductor 106 connects the outer terminal of the winding 22 to a contact brush 94, preming the shaft 10 in a manner hereinafter described, while a conductor 107 connects the inner terminal of the winding 24: to a similar contact brush 108 pressing lightly against the shaft 10. By reference to Figs. 2 and'3 of the drawings, it will be seen that the shaft 10 is divided and 102 firmly and rlgidly secured together by ascrew 90. A sleeve or collar 91 of inbone or the like, is threaded or suitably mounted on the screw and is firmly held between the abutting ends of the two parts of the shaft.

lightly against into two- Parts 101 maybe employed to. actuate .the plunger armature 20.

esa fixed stop 23. The

The sleeve 91 has a narrow radial slot in whlch is arranged a metallic contact strip vided with a peripheral groove 93 adaptedto accommodate the contact brushes 94 and 108. A third contact brush 95 bears lightly,

against one of the parts of the shaft 10and 1s electrically connected by a conductor 110v shaft 10, the brushes 95 and 108 are elec-.

trically connected when the contact strip 92 moves into engagement with-the brush .108. Qnce during each revolution of the shaft 10 the windings 22 and 24 .are successlvely electrically connected to one slde of closing device on the shaft.

Two fixed spring contacts 27 and .27, are

the mains 26 by the action of-the' circuitelectrically connected by a conductor '28 to the other side of the mains 26 from that to which the contact brush 95 is connected. A,

switching device comprising two parallel switching blades or arms 29 and 30 is adapted to be moved into electrical engagement with either the contact 27 or 27 "by a finger 33 preferably of insulating material secured to the carriage 15. The switch blades 29 and 30 are mechanically connected together by a link 32of insulating material.

7 It will thus be seen that the switch blade 29 electrically engages its coeperating contact 27 when the armature 20 engages stop 23, and that the switch blade 30 electrically engages the fixed contact 27 when the armature 20 is in. contact with its cooperating fixed stop 25. The switch blade 29 is connected by a conductor 86 to the inner ter minal of the solenoid winding 22, and the switch blade 30 is connected by a.conductor 87 to the outer terminal of the solenoid winding 24. It will be seen that the circuit of the winding 22 is broken when the switch blade 29 is withdrawn from the fixed contact 27, while on the other hand the circuit of the winding 24. is broken when. the switch blade 30 is withdrawn from the fixed contact 27. When the armature member 20 occupies its initial position the switch blade .it engages the fixed stop 25.

29 engages the contact 27 this being the position of-the elements illustrated in Fig. 1 of the drawings. When the contact strip 92 bridges the two brushes 94 and 95 the circuit of the winding 22 is completed and the armature: 20 is drawn toward the left until This movement of the armature throws the switch The sleeve and contact strip are pro-- blade SO intoengagement with the fixedcon-p tact 27' and withdraws the switch blade 29 from engagement with the fixed contact 27.

brings the contact strip 92 into'engagement with the contact brush 108 therebyclosing the "circuit ofthe winding 24 and-causing the armature 20 to be moved back to its initial position at the same time restoring the switch blades 29 and '30 to their respective initial positions. One revolution of the meter shaft thus c'auses the armature 20 and The next half revolution of the shaft 10 the elements attached thereto to make one complete reciprocal movement,whereby the pawl 13 operates: to drive the ratchet 12 through an angle corresponding to the pitch of one ratchet tooth. This cycle of operations is repeated eachtime the 10 makes one complete. revolution.

The spring contact fingers of the fixed contacts27 and-27". are so-designed that.

their coiiperating switch blades 29 and 30 respectively are' withdrawn just before the armature 20 engages stops 23 or 25. The contact strip 92 is furthermore of such width that the switching device always operates to withdraw one switch-blade from its contact and to throw the other switch fstrip moves out ofengagement" with the "brush 94 or thebrush 1.08, as the case may be, under allpossible speeds of the meter shaft. Thecircuit of the-solenoid windings.

22 and 24 is thus always broken by-the switching device and is never broken by the circuit-closing. device on the shaft 10. The

circuit-closing device on the meter shaft has very delicate contacts which would be.

A yoke 35 having two parallel guide rods 36 is pivotally mounted in the apparatus.

An actuator 37 is loosely mounted on the guide rods 36 and is biased by gravity to an initial position with the sleeve 38 resting against the base member 39 actuator carries a screw-threaded member 40 adapted to engage in the screw-threads of the shaftll, whereby rotation of the shaft in response to the driving action of the pawl 13 and ratchet 12 operates to move, the actu--. ator 37 upwardly.- A recording member 41 is also loosely mounted on the guide rods 36 and is biased by gravity to a position resting on the actuator 37. The recording member 41 carries at its as a pin point 42. A statfim'ary frame member 43 is. arranged in the path of travel of the pin point 42 and is adapted to have removably inserted therein a record sheet 44. An arm 45 is'secured to the yoke 35 and has securedthereto a spring46 which normally end a marking stylus, such meter shaft blade into its-contact before the contact of the yoke. Theacts to hold the member 40 of the actuator in operative. engagement with the screwthreads of the shaft 11. The magnetic plunger armature 47 of a solenoid winding 48 is secured to the arm 45, and when the solenoid winding is energized. the armature operates to rock the yoke 35 and to interrupt the op-. erative engagement of the actuator with the screw-threaded shaft 11. The circuit of the solenoid Winding 48 is controlled by a pair of coiiperating contacts 49 and 50. The contact 49 is fixed Whilethe contact 50 is driven at constant speed from any suitable constant speed driving mechanism such as a clockwork 51. The contact 50 is thus'timeactuated, and it therefore engages the contact 49 at equal time intervals.

The operation of the apparatus described i in the preceding paragraphs is as follows.

During each revolution of the metershaft 10 the contact strip 92 successively engages each of the contact brushes 94 and 108, there by effecting the successive energization of the solenoid windings 22 and 24. When the solenoid winding 22 is energized the arma; ture member 20 moves toward the left and the shaft 11 is turned through an angle corresponding to thetooth pitch of the, ratchet 12 The armature member 20 remains in this position until the shaft lOcompletes another half revolution, when the solenoid winding 24 is energized by the engagement of the contact strip 92 with the contact brush 108 and the armature member 20'is returned to its initial position. Each time the meter shaft 10 completes one revolution the shaft 11 is, therefore, rotated by the ratchet 12 and pawl 13 through ,an'angle'corr'esponding to the tooth pitch ofthe'ratchet. The spring 34 prevents overthrow of the ratchet during thedriving action by the pawl. Rotation of the shaft 11 moves the actuator 37 upwardly on the guides 36. The upward movement of the actuator 37 is thus proportional to the number of revolutions made by the meter shaft and is hence a measure of the amount of energy metered. The record ing member 41 is loosely mounted on the guide rods 36 and rests upon the actuator 37 and is hence moved upwardly withthe actuator, At the end 5f a predetermined time interval the time-actuated contact 50 enthe winding 48 is-deenergized, the spring 46 rocks the yoke 35 int'o'its normal position with the actuatpr'37 in operative engagement with theshaft 11 and withdraws the pin point 42 from the record sheet 44. The recording member 41 thereupon drops to its initial position resting upon the actuator 37. The engagementof the contacts 49 and 50 is maintained for a sufficient length of time to allow the actuator 37 to drop to its initial position before the solenoid winding 48 is deenergized. Since the actuator drops to its initial position substantially instantaneously upon t e energizing of this winding, it will be obvious that the winding needs to be energized for only a Very shorttime interval.

.In Fig. 4 of the drawings I have shown a pawl 60 mounted on a resilient spring arm 61 and secured to a carriage 62, the latter in turn being secured to the rod 16. In the modification illustrated in this figure the actuator and recording member are combined ina unitary structure This structure comprlses a frame member-63 loosely mountgage the screw' threads on the shaft 11 and inarkingpin point 67, ada ted to impart a record-mark on the recor sheet 44. The

guide rods 64;are secured together by end ,-,members 68 and, 69. A spring 70 bears against the end member 68 and normally maintains the member 66 in operative engagement with the shaft 11. A pairof electromagnets 71 have their windings connected in series and their common circuit controlled by the. cotip'eiating contacts 49 and 50. The armature 72 ,of these electromagnets is pivotally mounted and has secured thereto a bar 73. When the electromagnets 71 are energized the armature 72 moves the bar 73 into engagement with the outer end of the arm 65 thereby causing the pin point i 67 to impart a record mark on I the record sheet 44 and simultaneously interrupting the operative engagement of the member 66 ,with the shaft 11. A pair of electromagnets 74 have a cotiperating armature 75 secured to. the upper end member 69, and While these electromagnets are energized the member 66 is maintained operatively disengaged from the shaft 11. 'The circuit of the windings of the electromagnets 74 includes a pair of coiiperating contacts 76 and 77 and a second pair of coiipe'rating contacts 78 and 79. The contacts 78 and 79 are normally closed, and are. only open when the frame member 63 occupies its initial position resting upon the lower end member 68. -Contact 7 6.is sta tionary While itsboiiperating contact 77 is v secured to the end member 69. When the electromagnets 71 are energized the Hide "rods 64 are, rocked and the contact 7 is moved into engagement with the contact 76,

of operative engagement with the shaft 11."

As soon as'the electroma-gnets 71 are deenergizedthe bar 73 moves away fromthe arm 65 and the pin point 67 withdraws from the record sheet .44.- Theactuator then re" g the pro ect1on 105 electrical contact 1s made.

spending to the action-of gravity returns to itsinitial position. Just before reaching its initial position the framemember 63 of the actuatonstrikes a pin 80 secured to the movable contact79, and this contact is thereupon withdrawn from engagement with its cooperating fixed contact 7 8. The circuit of the electromagnets 74 is thereby opened and the spring 70 forces the member 66 again into operative engagement with the shaft 11. It will be evident, however, that positive means are provided for maintaining the actuator and the shaft disengaged until the actuator has returned to its initial position.

The contact 7 7 is more or less resilient and is so designed that when held in normal engagement vwith its cooperating contact 76 by the energization of. the electromagnets 74, the armature 75 is separated from the poles of .the electromagnets 74 by a small air gap and so that the pin point 67 is just out of engagement with the record 'sheet. The action of the bar- 73 upon the energization of the electromagnets 71 is to place the contact 77 under a slight tension so that the width of the air gap between the armature 75 and the poles of the electromagnets 74 is slightly less than when the magnets 71 are d energized, whereby the pin point 67 is forced into the record sheet. When the electromagnets71 are denergized the resiliency of the contact 77 acts to withdraw the pin point from the record sheet and permits the unobstructed passage of the actuator 63' and trated in Fig. 1. The shaft 10 is here also divided into two parts 101 and 102 secured together by a screw 98. or hub 99 0f insulating material surrounds the screw 98 and abuts the end of the part 101 of the shaft. A metallic collar 100 is mounted on the hub 99 and is insulated rigidly thereby both from the shaft and the screw.

A washer 103 of insulating material separates the collar 100 from the end of the other part 102 of the shaft 10. The collar 100 and the Washer 103 are each provided with a peripheral groovefto accommodate the contact brushes. The washer 103 has a narrow radial slot 104 into which extends a ])IO]60tl0n 105 of the collar 100. The projection 105 serves as a contact strip to bridge A bushing the normal demand. The the top of the record sheet indicate the abnormally l'arge demands, and it is in these demands that the central station manage-' of the equality of abnormal the contacts 96 and 97 or 96 and 109, as the between that brush and the other brush 96,

as will be readily understood. During each revolution of the shaft 10 the contact brushes 96 and 97 and the contact brushes 96 and 109 are'thus successively bridged by the projeca tion or contact stri 105 and the windings '22 and 24 successive y energized. The operation of the circuit-closing device, the switching device and the transmission of the motion of the meter shaft 10 to the rotatable screw-threaded shaft 11 are substantially the same in the apparatus of Fig. 4 as explained in connection with theapparatus of Fig. 1. It will be evident, however, that the brushes 96, 97 and 109 are always insulated from the meter shaft 10 and hence the shaft is neither alive nor grounded.

The record sheet 44 may be of any suit able material upon which a prick mark can be impressed by the pin point of the marking stylus. It will be understood that I do not desire to limit myself,to'the particular means of recording herein illustrated and described. I have, accordingly, employed the phrase record sheet in the appended claims to cover any device upon which a record may be made. The record sheet 44 is removably positioned in the frame member 43 so that a renewal of the record sheet may be made when desired.

The prick marks on the record sheet indicate the demand of the electrical installation in a simple and convenient form. At the end of each equal time interval a prick mark is made on the record eet and its height is a measure of the." amount of energy consumed and metered during the preceding time interval. The prick marks thus indicate the amounts of energy consumed and tervals of a substantiallength or duration.

In the case of the ordinary electrical .installation, the majority of the prick marks will be made on the record sheet at about the same position. This congested portion of the record sheet indicates the magnitude of rick marks at ment is most particularly interested. It will be .evident that the maximum demand is indicated by the prick mark nearest the top of the record sheet. The probability demands is such that there is likely to be few, if any, coincident prick marks in the upper portion of the record sheet. For this reason it is possible to obtain from the record sheet a substantially accurate and correct record of the abnormal demands of the installation, bothas to the frequency of occurrence and the magnitude of such demands.

It will be readily understood by those skilled in the art that the demand apparatus .of my present invention may be used if desired to measure the demand of an electrical installation in terms of the time required to consume a predetermined quantity of energy. When the apparatus is employed in this manner the contacts 94 and 95 or 96 and 97, as'the case may be, will be electrically in engagement at equal time intervals. The contacts i9 and 50 will in this case be controlled by the rotatable shaft of the meter, and will be closed at equal intervals of metered energy.

I have explained my invention by illustrating and describing certain specific embodiments thereof, but it will be readily understood by those skilled in the art that' the invention may be embodied in many other forms than that shown and described.

I, accordingly,do not wish to be restricted to the particular forms or constructions disclosed herein by way of example for the purpose of setting forth my invention in accordance with the patent statutes. The terms of the appended claims are, therefore, not restricted to the precise structures disclosed, but are intended to cover all changes and modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is

l. A demand apparatus comprising in combination a rotatable shaft, an actuator,

a reciprocating member adapted to drive said actuator only when moved in one direction, electromagnetic means controlled by said shaft for moving said member in the direction to drive said actuator, and additional electromagnetic means for moving the member in the opposite direction.

2. A demand apparatus comprising in combination a rotatable shaft an electric circuitincluding circuit-closing means operatively related to said shaft, an actuator,

electromagnetic means included in said circuit, an armature having an initial position and adapted to be moved therefrom and to drive said actuator upon the energization of said electromagnetic means, and electromagnetic means for returning the armature to its initial position.

3. A demand apparatus comprising in combination a rotatable shaft, a driving member, a ratchet secured to. said driving member, a reciprocating pawl operativelyrelated .to said ratchet, electromagnetic means controlled by said shaft for moving said pawl in the direction to drive said ratchet, and electromagnetic means also controlled by said shaft for moving the pawl in the opposite direction.

4. A demand ap aratus comprising in combination a rotata 1e shaft, an actuator, a reciprocating member adapted to drive said actuator when moved in one direction only, electromagnetic means for moving said member in the direction to drive said actuator and for moving said member in the opposite direction, main circuit-controlling means operatively related to said shaft for closing the circuits of said electromagnetic means, and auxiliary circuit controlling means operatively related to said member for opening the circuits of said electromagnetic means.

5; A demand apparatus comprising in combination a rotatable shaft, an actuator, a reciprocating member adapted to drive said actuator when moved in one direction only, electromagnetic means for moving said member in the direction to drive said actuator, main circuit-controlling means opercombination a rotatable shaft, an actuator, a

reciprocating member adapted "to drive said actuator when moved in one direction, an electromagnetic element adapted when energized to move said member in the direction to drive said actuator, a second electromagnetic element adapted when energized to move said member in the opposite direction, circuit-closing means operatively related to said shaft for successively closing the circuits of said electromagnetic elements, and circuit-opening means independent of said circuit-closing means operatively related to said member for successively opening the circuits of said electromagnetic elements.

7. A demand .apparatus comprising in combination a rotatable shaft, an actuator, a pair of electromagnetic elements, an armature member for said elements operatively related to said actuator and arranged to be moved in one direction upon the energization of one of said elements and in the other direction upon the energiZation of the other element, circuit-closing means operatively related to said shaft and included in the ,electric circuits of each of said electromagnetic elements, and means independent of said circuit closing meansfor opening the circuits of each of said electromagnetic elements. a

8. A demand apparatus comprising in combination a rotatable shaft, an actuator, a reciprocating member having an initial position and adapted to drive said actuator when moved from such initial position, electromagnetic. means adapted when energized to move said member from its initial position to drive said actuator, circuit-closing means operatively related to said shaft and included in the electric circuit of said electromagnetic means, a second electromagnetic means adapted when energized to return said member to 1ts initial position, means for controlling the electric circuit of said second. electromagnetic means, and

tromagnetic means for moving said member' in the direction to drive said actuator, electromagnetic means for moving said member in the opposite direction, circuit-closing means operatively related to said shaft and adapted to successively close the circuits of said electromagnetic means, and means opera'tively related to said member for opening the circuit of each of said electromagnetic means after said circuit closing means has operated to close the circuit.

10. A demand apparatus comprising in combination a rotatable shaft, an actuator, a reciprocating member adapted to drive said actuator when. moved in one direction, electromagnetic means for moving said member in the directionto drive said actuator, electromagnetic means for moving said member inthe opposite direction, circuit-closing means operativelyrelated to said shaft and adapted to successively close the circuits of said electromagneticmeans, and a switching device operatively related to said movable "member and adapted to open the circuit of that electromagnetic means last energized by the action of said circu t-closing means and to close the circuit of that electromagnetic means to be next energized by the ac-- tion of said circuit-closing means.

11. A demand apparatus comprising in.

combination a rotatable meter shaft, arotatable screw-threaded shaft operatively re lated to. said meter shaft, an actuator having a normally biased initial position and adapted to operatively engage said screwthreaded shaft, a'recording member independent of said actuator having a normally biased initial position and adapted to be moved by said actuator across a suitable record sheet, and means for intermittently causing said recording .member to impart a record mark on said record sheet and for interrupting said actuator and said screw-threaded shaft the operative engagement of whereby said actuator returns to its initial positio 12. A demand apparatus comprising in combination a rotatable meter shaft, a rotatable screw-threaded shaft operativeiy related to said meter shaft, an actuator having an initial position and adapted to operatively engage said scre\\-'-threaded shaft, a recording member independent of said actuator and adapted to be moved thereby, means for intermittently interrupting the operative engagement of said actuator and said screwthreaded shaft, and means n-hereby saiLl actuator returns to its initial position each time the operative engagement of said actuator and said screw-threaded shaft is interrupted.

13. A demand apparatus comprising in combination a driving member, an actuator having a reciprocatory straight-line motion biased to an initial position 'and normally maintained in operative engagement with said driving member, a recording member having a reciprocatory straight-line motion biased to an initial position and adapted to be moved by said actuator, said recording member and said actuator being arranged to independently return to their respective ini-- tial positions, a stationary record sheet operatively related to said recording member, and means operating at the end of each of a number of intervals of a greater time duration than one-minutc for causing said recording member to impart a record mark on said record sheet and to interrupt the operative engagement of said actuator and said driving member thereby permitting the actuator to return to its initial position. 14. A demand apparatus comprising in combination a rotatable meter shaft, a rotatable scrmv-threaded shaft operatirely related to said meter shaft, an actuator having a normally biased initial position and adapted to opcratively engage said screwthrcadcd shaft. :1 recording member lndependent of saidactuator having a normally biased initial position and adapted to be moved by said actuator, a stationary frame -member arranged in the path of travel of initial position.

15. A demand apparatus comprising in combination a driving member, a guide rod, an actuator loosely mounted on said rod and biased to an initial position, means whereby 'said actuator is normally held in engagement With said driving member, a recording member independent of said actuator and adapted to be moved thereby, and means for rocking said guide rod to interrupt the operative engagement of said actuator and said driving member thereby permitting the actuator to return to its initial position.

16. A demand apparatus comprising in combination a driving member, a guide rod, an actuator loosely mounted on said rod and biased to an initial position, means whereby said actuator is normally held in engagement withsaid driving member, a recording member also biased to an initial .position and adapted 'to be moved by said actuator, a record sheet operatively related to said recording member, and means for intermittently rocking said guide rod to cause said recording member to impart a record mark on said record sheet and to interrupt the operative engagement of said actuator and said driving member thereby permitting the actuator to return to its initial position.

17. A demand apparatus comprising in combination a driving member, a guide rod, an actuator loosely mounted on said rod and biased by gravity to an initial position, means whereby said actuator is normally held in engagement with said driving member, a recording member also loosely mounted on said rod and biased by gravity to an initial positionand adapted to be moved by said actuator, a record sheet operatively related to said recording member, and means for intermittently rocking said guide rod to cause said recording member to impart -a record mark on said record sheet and to interrupt the operative engagement of said actuator and said driving member thereby permitting the actuator to return to its initial position.

18. A demand apparatus comprising in combination a rotatable screw threaded shaft, a pivotally mounted yoke having two parallel guide rods, an actuator mounted on said guide rods and biased to an initial position, means whereby said actuator is normally held in operative engagement with said shaft,- a recording member adapted to be moved by said actuator, and means for rocking said yoke to interrupt the operative engagement of said actuator and said shaft thereby permitting the actuator to re turn to its initial position.

19. A demand apparatus comprising in combination a rotatable screw-threaded shaft, a pivotally mounted yoke having two parallel guide rods, an actuator mounted on said guide rods and biased to an initial position, means whereby' said actuator 'is normally held in operative engagement with said shaft, means for rocking said yoke to interrupt the operative engagement of said actuator and said shaft thereby permitting the actuator to return to its initial position, and positive means for maintaining said actuator and said shaft operatively disits initial position.

20. A demand apparatus comprising in combination a rotatable screw-threaded shaft, a pivotally mounted yoke having two parallel guide rods, an actuator mounted on said guide rods and biased to an initial position, means whereby said actuator is normally held in operative engagement with said shaft, a recording member mounted on said guide rods and adapted to be moved by said actuator, a record sheet operatively related to said recording member, and means for rocking said yoke to cause said recording member to impart a record mark on said record sheet and to interrupt the operative engagement of said actuator and said shaft thereby permitting the actuator to return to its initial position.

21. A demand apparatus comprising in combination a rotatable screw-threaded shaft, a pivotally mounted yoke having two parallel guide rods, an actuator loosely mounted on said guide rods and biased by gravity to an initial position, means whereby said actuator is normally held in operative engagement with said shaft, a recording member loosely mounted on said guide rods above said actuator and adapted to be moved thereby, and means for rocking said yoke to interrupt the operative engagement of said actuator and said shaft thereby permitting the actuator to return to its initial position.

22. A demand apparatus comprising in combination a rotatable screw-threaded shaft, a pivotally mounted yoke having two parallel guide rods, an actuator loosely mounted onsaid guide rodsand biased by gravity to an initial position, means whereby said actuator is normally held in operative engagement with said. shaft, a recording member also loosel ounted onsaid guide rods above said actuator and biased by gravity to an initial position and adapted to be moved by said actuator, a record sheet operatively related to said recording member, and means for rocking said yoke to said screw-threaded vshaft, a pivotally mounted yoke having two parallel guide rods, an actuator loosely mounted on said guide rods and biased to an initial position, means whereby said actuator is normally held in operative engagement with said shaft, a recording member also loosely mounted on said guide rods above said actuator and biased by gravity to an initial position and adapted to be moved by said actuator, a rec-' 0rd sheet operatively related to said re-' cording member, 1 means including a time-actuated circuit opand electromagnetic erating device for rocking said yoke to cause said recording member toimpart a record mark on said record sheet and to interrupt the operative engagement of said actuator JOHN T. DEMPSTER.

Witnesses:

HELEN ORFORD, I MARGARET WOOLLEY. s 

